My Dad is the exact same way. Mainly because his LL team was the Pirates, but up until the Colt 45/Astros showed up, Pittsburgh was the team he followed.
i was a Brooklyn Dodgers fan originally, but when they went to LA, they jilted me. i started following the Pirates as "my" team in 1959, primarily because of Face's 18-1 season. by ST 1960, i was hooked and started my day with intense review of the story and box score. occasionally, the Pirates would be on Mutual's Game of the Day on radio or on TV, but most of my being a Pirates fan was through the newspapers. what a team! what a season! what a WS! What a Game 7!
whenever i could choose the name/cap of the kids' teams i coached, we were the Pirates. Mark and i have 5 years of Pirates caps somewhere. we always got a Pirates cap for my Dad, and he went to Heaven wearing one. i often wondered what folks at his funeral thought about that, but it was normal to us. he was my best pitching coach ever and was a big fan of Mark's progress in baseball. my one regret is that he did not live to see the 97 Knights.
when the Colt .45s entered the NL in 1962, i switched my allegiance to Houston, and the rest, as they say, is history.